User`s guide

68
Chapter 3 System Overview
Data Acquisition System Overview
Transducers and Sensors
Transducers and sensors convert a physical quantity into an electrical
quantity. The electrical quantity is measured and the result is then
converted to engineering units. For example, when measuring a
thermocouple, the instrument measures a DC voltage and
mathematically converts it to a corresponding temperature in °C, °F, or
K.
Measurement Typical Transducer Types Typical Transducer Output
Temperature Thermocouple 0 mV to 80 mV
RTD 2-wire or 4-wire resistance
from 5 to 500
Thermistor 2-wire resistance from
10 to 1 M
Pressure Solid State +/-10 VDC
Flow Rotary Type
Thermal Type
4 mA to 20 mA
Strain Resistive Elements 4-wire resistance from 10 to
10 k
Events Limit Switches
Optical Counters
Rotary Encoder
0V or 5V Pulse Train
Digital System Status TTL Levels
34970A Refresh UG.book Page 68 Wednesday, February 17, 2010 12:34 PM